I would try a batch and see what happens. Because when I color ivory fondant, the color doesn't turn out the same as it usually would. Obviously, fondant and cream cheese are different, but they are both ivory.

And if you practice now, you can at least warn your bride that it's not going to be the exact shade that she wants it to be. Or suggest that she go with a different frosting.

Definitely test a small batch first. Because of the yellow-ish tint (ivory) of the cream cheese icing, adding just straight teal MIGHT result in something that has more of a green tint, so test it to see if you have to alter it any.